Pool the buffer and encoder used for generic JSON reflection (#602)

Pool buffers and encoders to make JSON reflection less expensive.

buffer/buffer.go

@@ -98,6 +98,15 @@ func (b *Buffer) Write(bs []byte) (int, error) {
 	return len(bs), nil
 }
 
+// TrimNewline trims any final "\n" byte from the end of the buffer.
+func (b *Buffer) TrimNewline() {
+	if i := len(b.bs) - 1; i >= 0 {
+		if b.bs[i] == '\n' {
+			b.bs = b.bs[:i]
+		}
+	}
+}
+
 // Free returns the Buffer to its Pool.
 //
 // Callers must not retain references to the Buffer after calling Free.

zapcore/json_encoder.go

@@ -44,10 +44,15 @@ func getJSONEncoder() *jsonEncoder {
 }
 
 func putJSONEncoder(enc *jsonEncoder) {
+	if enc.reflectBuf != nil {
+		enc.reflectBuf.Free()
+	}
 	enc.EncoderConfig = nil
 	enc.buf = nil
 	enc.spaced = false
 	enc.openNamespaces = 0
+	enc.reflectBuf = nil
+	enc.reflectEnc = nil
 	_jsonPool.Put(enc)
 }
 
@@ -56,6 +61,10 @@ type jsonEncoder struct {
 	buf            *buffer.Buffer
 	spaced         bool // include spaces after colons and commas
 	openNamespaces int
+
+	// for encoding generic values by reflection
+	reflectBuf *buffer.Buffer
+	reflectEnc *json.Encoder
 }
 
 // NewJSONEncoder creates a fast, low-allocation JSON encoder. The encoder
@@ -124,13 +133,24 @@ func (enc *jsonEncoder) AddInt64(key string, val int64) {
 	enc.AppendInt64(val)
 }
 
+func (enc *jsonEncoder) resetReflectBuf() {
+	if enc.reflectBuf == nil {
+		enc.reflectBuf = bufferpool.Get()
+		enc.reflectEnc = json.NewEncoder(enc.reflectBuf)
+	} else {
+		enc.reflectBuf.Reset()
+	}
+}
+
 func (enc *jsonEncoder) AddReflected(key string, obj interface{}) error {
-	marshaled, err := json.Marshal(obj)
+	enc.resetReflectBuf()
+	err := enc.reflectEnc.Encode(obj)
 	if err != nil {
 		return err
 	}
+	enc.reflectBuf.TrimNewline()
 	enc.addKey(key)
-	_, err = enc.buf.Write(marshaled)
+	_, err = enc.buf.Write(enc.reflectBuf.Bytes())
 	return err
 }
 
@@ -213,12 +233,14 @@ func (enc *jsonEncoder) AppendInt64(val int64) {
 }
 
 func (enc *jsonEncoder) AppendReflected(val interface{}) error {
-	marshaled, err := json.Marshal(val)
+	enc.resetReflectBuf()
+	err := enc.reflectEnc.Encode(val)
 	if err != nil {
 		return err
 	}
+	enc.reflectBuf.TrimNewline()
 	enc.addElementSeparator()
-	_, err = enc.buf.Write(marshaled)
+	_, err = enc.buf.Write(enc.reflectBuf.Bytes())
 	return err
 }
 

zapcore/json_encoder_test.go

@@ -0,0 +1,122 @@
+// Copyright (c) 2018 Uber Technologies, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+package zapcore_test
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+
+	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
+)
+
+// TestJSONEncodeEntry is an more "integrated" test that makes it easier to get
+// coverage on the json encoder (e.g. putJSONEncoder, let alone EncodeEntry
+// itself) than the tests in json_encoder_impl_test.go; it needs to be in the
+// zapcore_test package, so that it can import the toplevel zap package for
+// field constructor convenience.
+func TestJSONEncodeEntry(t *testing.T) {
+	type bar struct {
+		Key string  `json:"key"`
+		Val float64 `json:"val"`
+	}
+
+	type foo struct {
+		A string  `json:"aee"`
+		B int     `json:"bee"`
+		C float64 `json:"cee"`
+		D []bar   `json:"dee"`
+	}
+
+	tests := []struct {
+		desc     string
+		expected string
+		ent      zapcore.Entry
+		fields   []zapcore.Field
+	}{
+		{
+			desc: "info entry with some fields",
+			expected: `{
+				"L": "info",
+				"T": "2018-06-19T16:33:42.000Z",
+				"N": "bob",
+				"M": "lob law",
+				"so": "passes",
+				"answer": 42,
+				"common_pie": 3.14,
+				"such": {
+					"aee": "lol",
+					"bee": 123,
+					"cee": 0.9999,
+					"dee": [
+						{"key": "pi", "val": 3.141592653589793},
+						{"key": "tau", "val": 6.283185307179586}
+					]
+				}
+			}`,
+			ent: zapcore.Entry{
+				Level:      zapcore.InfoLevel,
+				Time:       time.Date(2018, 6, 19, 16, 33, 42, 99, time.UTC),
+				LoggerName: "bob",
+				Message:    "lob law",
+			},
+			fields: []zapcore.Field{
+				zap.String("so", "passes"),
+				zap.Int("answer", 42),
+				zap.Float64("common_pie", 3.14),
+				zap.Reflect("such", foo{
+					A: "lol",
+					B: 123,
+					C: 0.9999,
+					D: []bar{
+						{"pi", 3.141592653589793},
+						{"tau", 6.283185307179586},
+					},
+				}),
+			},
+		},
+	}
+
+	enc := zapcore.NewJSONEncoder(zapcore.EncoderConfig{
+		MessageKey:     "M",
+		LevelKey:       "L",
+		TimeKey:        "T",
+		NameKey:        "N",
+		CallerKey:      "C",
+		StacktraceKey:  "S",
+		EncodeLevel:    zapcore.LowercaseLevelEncoder,
+		EncodeTime:     zapcore.ISO8601TimeEncoder,
+		EncodeDuration: zapcore.SecondsDurationEncoder,
+		EncodeCaller:   zapcore.ShortCallerEncoder,
+	})
+
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			buf, err := enc.EncodeEntry(tt.ent, tt.fields)
+			if assert.NoError(t, err, "Unexpected JSON encoding error.") {
+				assert.JSONEq(t, tt.expected, buf.String(), "Incorrect encoded JSON entry.")
+			}
+			buf.Free()
+		})
+	}
+}